Decreased levels of ____(a)____ is a common cause for osteoporosis in _____(b)_____. 

In the above statement, (a) and (b) are

Oestrogen helps regulate the balance between bone formation and bone resorption (breakdown). 

• Stimulation of Osteoblasts: Estrogen has a direct stimulatory effect on osteoblasts, promoting their activity. This results in increased bone formation and deposition of new bone matrix.
• Inhibition of Osteoclasts: Estrogen helps regulate osteoclasts, which are cells responsible for bone resorption (breakdown). By reducing the number and activity of osteoclasts, estrogen helps to slow down bone resorption and maintain bone density.

Before menopause, estrogen levels in women are relatively stable and help preserve bone density. However, during menopause, there is a significant decrease in estrogen production due to the cessation of ovarian function.

The decline in oestrogen levels leads to an increase in bone resorption, meaning that bones are broken down faster than they are built up. This results in a decrease in bone mass and density, making the bones weaker and more susceptible to fractures. As a result, postmenopausal women have a higher risk of developing osteoporosis.

Other factors can also contribute to osteoporosis, such as inadequate calcium and vitamin D intake, sedentary lifestyle, certain medications, and certain medical conditions. However, decreased estrogen levels during and after menopause are a significant risk factor for osteoporosis in women.